Interpretive Summary: Stable flies are among the most important pests of cattle and other livestock in North America. Their biting and annoyance reduce weight gains in cattle costing producers more than $2 billion per year in production losses. The spatial and temporal dynamics of stable fly populations are poorly understood. We examined the spatial distribution of stable flies across a diversified agricultural environment in eastern Nebraska. Stable fly populations were found to fluctuate on a relatively fine scale. Traps as close as 1.6 miles apart were temporally asynchronous. Proximity of traps to confined livestock facilities affected both the level and seasonal patterns of catches. The range of influence of such facilities was less than 1 mile. The variability among trap catches indicated that a larger number of traps located closer together than previously expected is needed to evaluate population levels and dynamics of this pest.

Technical Abstract:
Spatial and temporal relationships among catches of adult stable flies on sticky traps in eastern Nebraska were evaluated. Twenty-five alsynite sticky traps were placed in a 5 × 5 grid with ˜1.6 km intervals in a mixed agricultural environment from 2003 to 2011. Denser grids of 45-90 traps were implemented for varying lengths of time during the course of the study and six traps were maintained in 2001 and 2002. More than 2 million stable flies were collected over 11 years. Seasonal abundances based upon total collections from the primary grid of 25 traps were bimodal most years with population peaks in June and September or October. Individual trap catches varied greatly, both spatially and temporally. Spatial autocorrelation of catches was observed up to ˜2 km. Trap catches were spatially aggregated. Synchrony among trap catches declined linearly with respect to distance between traps and differences in seasonal distribution increased asymptotically relative to distance between traps. Proximity to confined livestock facilities increased catch and proportion of catch collected later in the season. Fifteen to 20 traps were adequate for estimating stable fly populations with a confidence level of having the standard error of the mean be within 30% of the mean for most of the stable fly season. Early and late in the season when mean trap catches were low, between 100 and 135 traps would be needed to maintain that level of confidence. Seasonal collection distributions from permutations with fewer than 24 traps differed significantly from those of the complete grid of 25 traps.